Hybrids aside, BMW has its low-carbon quota absolutely filled. Its 2.0-litre diesel engine, in various power outputs, has been offering a great balance of performance and efficiency in almost every model in the range. Hybrids are still a relative niche, and BMW simply doesn’t need to chase the technology until taxation and environmental policies make diesels a harder sell. It’s safe for now.

So the ActiveHybrid versions of the 3 Series, 5 Series and 7 Series have instead focused on offering some of the highest power outputs in their segments, but with fuel efficiency far below conventional large petrols. In short, it makes BMW’s smooth and powerful six-cylinder petrol engine much more palatable for business drivers.

The drivetrain uses a 3.0-litre twin-turbocharged engine and disc-shaped electric motor sandwiched between this and the eight-speed transmission. Visually there’s very little to mark this out as anything unusual, no dinner-plate aerodynamic wheels or blue glows around the BMW badges to shout about the technology inside.

It’s also available in two trim levels, including the M Sport version tested here, which looks aggressive but pushes fuel efficiency down from 44.1mpg to 40.4mpg with a corresponding jump in CO2 emissions from 149 to 163g/km.

At a combined 340bhp, though, this offers nearly twice the power of the range-favourite 520d. The gearbox tends to prioritise higher gears for economy purposes, but with a few tugs of the left hand steering wheel paddle there’s a glut of power available for overtaking. On paper, at least, it’s a direct match for the 535i Automatic, which is only £6,000 cheaper and at 183g/km it’s four BiK bands higher.

Drive modes ranging from the sharpest Sport+, with disengaged traction control, down to the electric-prioritising ECO PRO, are selected using the familiar rocker switch on the centre panel with Comfort chosen as a default. The battery charges quickly while driving, and it’s relatively easy to keep it running on electricity around flat inner-city routes which is a real novelty. It’s difficult not to see the appeal of wafting along in complete silence in a car as luxurious as this.

But it’s worth watching the Hybrid display to really get a feel how clever the system is. Imperceptible at high speeds, the electric motor kicks in intermittently to give the petrol engine a boost and reduce the fuel it uses. Stab at the throttle and average fuel economy plummets, but it’s so powerful that it’s also easy to drive this smoothly and steadily with the engine barely ticking over. Enforce a 70mph limit to stop the speed creeping up and in ECO PRO mode it’ll be nudging 40mpg on the motorway.

There are downsides, though. As fast as the ActiveHybrid 5 is, it’s not really a driver’s car. Regenerative braking through the motor gives a two-stage feel to the brakes, so you do have to press quite hard to get a mechanical bite. There’s also a large sacrifice in boot space, with a large area immediately behind the seats taken up by the battery.

So a low carbon M5 this isn’t, but for long effortless motorway journeys it’s a blissfully easy way to get around. BMW has no illusions that this will pull the rug out from under the 520d, but it makes that iconic straight-six engine tax efficient for the technology-savvy company car driver.

Verdict:

With an appealing family of low carbon, high-performance diesels, BMW’s ActiveHybrid models will only ever be niche sellers in the UK, making sense only when considered as a tax-conscious alternative to a conventional big-power petrol. Technology rich, and clever with it, early adopters with a taste for effortless cruising could find this an irresistible and exclusive option.

Spec:

Segment: Executive

Type: Petrol-electric hybrid

Price: £44,045

Fuel: 40.4mpg

Electric range: 2.4 miles

CO2 emissions (tailpipe): 163g/km

Charging Port: N/A